EXPLAIN and nfiltered, take two

Hi,

Here's a patch for $SUBJECT based on the feedback here:
http://archives.postgresql.org/message-id/9053.1295888538@sss.pgh.pa.us

I intentionally decided to omit the information for Join Filter, since
the information can already be deduced from EXPLAIN ANALYZE output, and
for Left Joins and Anti Joins "Rows Removed by Join Filter" didn't
really make much sense.

The "Rows Removed by .." information is always shown by default (when
there is a Filter or Recheck Cond, of course), and I didn't feel like it
was worth it to add a new option for EXPLAIN to turn that information off.

As for documentation.. I'm really at a loss here. I tried numerous
different things for doc/src/sgml/perform.sgml, but I didn't feel like
any of them added anything. The EXPLAIN ANALYZE output seems quite
self-explanatory after all.

Attached are also the tests I used, and an example output.

--
Marko Tiikkaja http://www.2ndQuadrant.com/
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